Retrievable stent system

ABSTRACT

A system for treating a body lumen including a first stent configured to be positioned in a body lumen and a second stent configured to be positioned in the lumen of the first stent prior to removing the first stent from the body lumen. The first stent includes a liner disposed radially inward of the tubular scaffold of the first stent to permit tissue ingrowth within a tissue ingrowth region defined between the liner and the tubular scaffold. The retrieval stent is configured to be expanded within the previously implanted first stent to cause tissue to recede from the tissue ingrowth region to facilitate removal of the first stent from the body lumen.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.15/936,651, filed Mar. 27, 2018, which claims priority to U.S.Provisional Application Ser. No. 62/477,737, filed Mar. 28, 2017, theentirety of which is incorporated herein by reference.

TECHNICAL FIELD

The present disclosure pertains to medical devices, methods formanufacturing medical devices, and the use thereof. More particularly,the present disclosure pertains to stents designed to be removed fromthe body and methods for manufacturing and using such stents.

BACKGROUND

Implantable medical devices (e.g., expandable stents) may be designed toprovide a pathway for digested material, blood, or other fluid to flowtherethrough following a medical procedure. Further, some implantablemedical devices may incorporate features that aid in fistula treatment,bypass procedures and/or anastomosis treatment. These medical devicesmay include radially or self-expanding stents which may be implantedtransluminally via an endoscope. Additionally, some stents may beimplanted in a variety of body lumens such as the esophageal tract, thegastrointestinal tract (including the intestine, stomach and the colon),tracheobronchial tract, urinary tract, biliary tract, vascular system,etc.

In some instances it may be desirable to design a stent which includessufficient radial strength to maintain its position within a body lumenwhile also having the ability to function as a passageway for food orother digested material to flow therethrough. However, in some stents,the compressible and flexible properties that assist in stentpositioning may also result in a stent that has a tendency to migratefrom its originally deployed position. For example, stents that aredesigned to be positioned in the esophageal or gastrointestinal tractmay have a tendency to migrate due to peristalsis (i.e., the involuntaryconstriction and relaxation of the muscles of the esophagus, intestine,and colon which push the contents of the canal therethrough).Additionally, the generally moist and inherently lubricious environmentof the esophagus, intestine, colon, etc. further contributes to astent's tendency to migrate when deployed therein. One method to reducestent migration may include exposing bare metal portions of the stent tothe tissue of the body lumen. The stent scaffold may provide a structurethat promotes tissue ingrowth into the interstices or openings thereof(e.g., the stent structure may promote a hyperplastic response). Thetissue ingrowth may anchor the stent in place and reduce the risk ofstent migration.

Additionally, while it is important to design stents that reduce thedegree to which a stent migrates within a body lumen, it also importantto design stents that may be easily removed and/or re-positioned fromthe body lumen post-deployment. Stents including bare portions (i.e.,uncovered portions) designed to promote tissue ingrowth (e.g., to reducestent migration as described above) may also be more difficult to removeonce the tissue has anchored the stent in the body lumen. One method toreduce the force necessary to remove a stent from a body lumen mayinclude positioning a covered, expandable secondary stent within thelumen of the primary (e.g., anchoring) stent. The radial expansion ofthe secondary stent within the lumen of the primary stent may cause thetissue ingrowth to recede, thereby reducing the force necessary toremove both the primary and secondary stents from the wall of the bodylumen. Examples of secondary medical devices which are capable of beingutilized with other medical devices are disclosed herein.

BRIEF SUMMARY

This disclosure provides design, material, manufacturing method, and usealternatives for medical devices. An example system for treating a bodylumen includes a first stent. The first stent includes a first tubularscaffold, the first tubular scaffold including an inner surface. Thefirst stent also includes an outer surface and a lumen extendingtherethrough and a liner disposed within the lumen of the first tubularscaffold, wherein the liner is configured to be radially spaced from theinner surface of the first tubular scaffold to permit tissue ingrowthalong a portion of first tubular scaffold. The system also includes asecond stent. The second stent includes a second tubular scaffold and acovering disposed on the second tubular scaffold, wherein the secondstent is configured to be positioned within the first stent such thatexpansion of the second stent causes the tissue ingrowth to recede.

Alternatively or additionally to any of the embodiments above, whereinthe second tubular scaffold is configured to expand radially outward,and wherein the radially outward expansion of the second tubularscaffold causes the tissue ingrowth to recede.

Alternatively or additionally to any of the embodiments above, whereinthe first stent includes an inner surface having a first profile, andwherein the second stent includes an outer surface having a secondprofile, and wherein the first profile matches the second profile.

Alternatively or additionally to any of the embodiments above, whereinthe second stent includes a first end region and a second end region,and wherein the first end region, the second end region, or both thefirst and second end regions have a flared portion.

Alternatively or additionally to any of the embodiments above, whereinthe liner is configured to be radially spaced from a medial region ofthe first tubular scaffold to permit a tissue ingrowth region along themedial region, and wherein the second stent is configured to exert aradially outward expansion force along the tissue ingrowth region,wherein the radially outward expansion force is sufficient to cause thetissue ingrowth to recede.

Alternatively or additionally to any of the embodiments above, whereinthe radially outward expansion force is 0.15 N or more.

Alternatively or additionally to any of the embodiments above, whereinthe liner is configured to limit the amount of tissue ingrowth into themedial region of the tubular scaffold due to a hyperplastic response.

Alternatively or additionally to any of the embodiments above, whereinthe tissue ingrowth region is formed between the inner surface of thetubular scaffold and an outwardly-facing surface of the liner.

Alternatively or additionally to any of the embodiments above, whereinthe portion of the liner extending along the tissue ingrowth region isconfigured to deflect radially inward from the inner surface of thetubular scaffold.

Alternatively or additionally to any of the embodiments above, whereinthe medial portion of the tubular scaffold includes a first innerdiameter, and wherein the diameter of the liner along the tissueingrowth region includes a second inner diameter, and wherein the secondinner diameter is greater than 25% of the diameter of the first innerdiameter.

Alternatively or additionally to any of the embodiments above, whereinthe tissue ingrowth region extends circumferentially around the innersurface of the tubular scaffold.

Alternatively or additionally to any of the embodiments above, wherein amedial region of the tubular scaffold of the second stent has an outerdiameter in a radially expanded state of the second stent greater thanan inner diameter along a medial region of the tubular scaffold of thefirst stent in a radially expanded state of the first stent.

Another system for treating the esophagus includes:

-   -   a first stent including:        -   a first expandable scaffold, the first expandable tubular            scaffold including an inner surface, an outer surface and a            lumen extending therein; and        -   a liner disposed within the lumen of the first expandable            scaffold, wherein the liner is configured to be radially            spaced from a medial region of the first expandable scaffold            to define a tissue ingrowth region along a portion of first            expandable scaffold; and    -   a second stent including:        -   a second expandable scaffold and a covering disposed on the            second expandable scaffold;    -   wherein the second stent is configured to be positioned within        the first stent such that expansion of the second stent causes        the tissue ingrowth to recede along the tissue ingrowth region.

Alternatively or additionally to any of the embodiments above, whereinthe second expandable scaffold is configured to expand radially outward,and wherein the radially outward expansion of the second expandablescaffold causes the tissue ingrowth to recede.

Alternatively or additionally to any of the embodiments above, whereinthe second stent is configured to exert a radially outward expansionforce along the tissue ingrowth region, wherein the radially outwardexpansion force is sufficient to cause the tissue ingrowth to recede.

Alternatively or additionally to any of the embodiments above, whereinthe radially outward expansion force is 0.15 N or more.

Alternatively or additionally to any of the embodiments above, whereinthe first stent includes an inner surface having a first profile, andwherein the second stent includes an outer surface having a secondprofile, and wherein the first profile matches the second profile.

Alternatively or additionally to any of the embodiments above, whereinthe portion of the liner extending along the tissue ingrowth region isconfigured to deflect radially inward from the inner surface of thetubular scaffold.

Alternatively or additionally to any of the embodiments above, whereinthe liner extends continuously within the lumen of the first expandablescaffold.

An example method of treating a body lumen includes:

-   -   advancing a retrieval stent into the lumen of an implanted stent        disposed along an inner surface of the body lumen, wherein a        portion of tissue defining the inner surface of the body lumen        has grown into the implanted stent, and wherein the implanted        stent includes:        -   a liner disposed within the lumen of the implanted stent,            wherein the liner is configured to be radially spaced from a            medial region of the implanted stent to define a tissue            ingrowth region along a portion of the implanted stent;    -   deploying the retrieval stent within the lumen of the implanted        stent, wherein an outer surface of the retrieval stent exerts an        outward radial force along the ingrown tissue region of the        implanted stent, and wherein the retrieval stent causes the        ingrown tissue to recede.

The above summary of some embodiments is not intended to describe eachdisclosed embodiment or every implementation of the present disclosure.The Figures and Detailed Description, which follow, more particularlyexemplify these embodiments.

BRIEF DESCRIPTION OF THE DRAWINGS

The disclosure may be more completely understood in consideration of thefollowing detailed description in connection with the accompanyingdrawings, in which:

FIG. 1 is an example stent;

FIG. 2 is a cross-sectional view of the stent of FIG. 1 including aliner taken along line 2-2 of FIG. 1;

FIG. 3 is a cross-sectional view of the stent of FIG. 1 taken along line3-3 of FIG. 2;

FIG. 4 is a cross-sectional view of the stent of FIG. 1 taken along line4-4 of FIG. 2;

FIG. 5 is a cross-sectional view of the stent of FIG. 1 including aliner;

FIG. 6A is a cross-sectional view of another example stent including aliner and covered portions;

FIG. 6B is a cross-sectional view of another example stent including aliner and covered portions;

FIG. 7A is a cross-sectional view of another example stent including aliner and covered portions;

FIG. 7B is a cross-sectional view of another example stent including aliner and covered portions;

FIG. 8A is a plan view of another example stent including a liner andcovered portions;

FIG. 8B is a plan view of another example stent including a liner;

FIG. 8C is a cross-sectional view of another example stent;

FIG. 9 is another example stent;

FIG. 10 is a cross-sectional view of the stent of FIG. 9 taken alongline 10-10 of FIG. 9;

FIGS. 11-13 illustrate an example stent positioned in a body lumenundergoing a hyperplastic response;

FIGS. 14-17 illustrate an example method for deploying an example stentwithin another example stent;

FIG. 18 illustrates the retrieval of the example stent systemillustrated in FIGS. 14-17.

While the disclosure is amenable to various modifications andalternative forms, specifics thereof have been shown by way of examplein the drawings and will be described in detail. It should beunderstood, however, that the intention is not to limit the disclosureto the particular embodiments described. On the contrary, the intentionis to cover all modifications, equivalents, and alternatives fallingwithin the spirit and scope of the disclosure.

DETAILED DESCRIPTION

For the following defined terms, these definitions shall be applied,unless a different definition is given in the claims or elsewhere inthis specification.

All numeric values are herein assumed to be modified by the term“about”, whether or not explicitly indicated. The term “about” generallyrefers to a range of numbers that one of skill in the art would considerequivalent to the recited value (e.g., having the same function orresult). In many instances, the terms “about” may include numbers thatare rounded to the nearest significant figure.

The recitation of numerical ranges by endpoints includes all numberswithin that range (e.g. 1 to 5 includes 1, 1.5, 2, 2.75, 3, 3.80, 4, and5).

As used in this specification and the appended claims, the singularforms “a”, “an”, and “the” include plural referents unless the contentclearly dictates otherwise. As used in this specification and theappended claims, the term “or” is generally employed in its senseincluding “and/or” unless the content clearly dictates otherwise.

It is noted that references in the specification to “an embodiment”,“some embodiments”, “other embodiments”, etc., indicate that theembodiment described may include one or more particular features,structures, and/or characteristics. However, such recitations do notnecessarily mean that all embodiments include the particular features,structures, and/or characteristics. Additionally, when particularfeatures, structures, and/or characteristics are described in connectionwith one embodiment, it should be understood that such features,structures, and/or characteristics may also be used connection withother embodiments whether or not explicitly described unless clearlystated to the contrary.

The following detailed description should be read with reference to thedrawings in which similar elements in different drawings are numberedthe same. The drawings, which are not necessarily to scale, depictillustrative embodiments and are not intended to limit the scope of thedisclosure.

As discussed above, in some instances it may be designed to provide apathway for digested material, blood, or other fluid to flowtherethrough following a medical procedure. Further, some implantablemedical devices may incorporate features that aid in fistula treatment,bypass procedures and/or anastomosis treatment. These medical devicesmay include radially or self-expanding stents which may be implantedtransluminally via an endoscope. Additionally, some stents may beimplanted in a variety of body lumens such as the esophageal tract, thegastrointestinal tract (including the intestine, stomach and the colon),tracheobronchial tract, urinary tract, biliary tract, vascular system,etc.

In some instances it may be desirable to design a stent which includessufficient radial strength to maintain its position within a body lumenwhile also having the ability to function as a passageway for food orother digested material to flow therethrough. However, in some stents,the compressible and flexible properties that assist in stentpositioning may also result in a stent that has a tendency to migratefrom its originally deployed position. For example, stents that aredesigned to be positioned in the esophageal or gastrointestinal tractmay have a tendency to migrate due to peristalsis (i.e., the involuntaryconstriction and relaxation of the muscles of the esophagus, intestine,and colon which push the contents of the canal therethrough).Additionally, the generally moist and inherently lubricious environmentof the esophagus, intestine, colon, etc. further contributes to astent's tendency to migrate when deployed therein. One method to reducestent migration may include exposing bare metal portions of the stent tothe tissue of the body lumen. The stent scaffold may provide a structurethat promotes tissue ingrowth (e.g., a hyperplastic response) into theinterstices or openings thereof. The tissue ingrowth may anchor thestent in place and reduce the risk of stent migration.

Additionally, while it is important to design stents that reduce thedegree to which a stent migrates within a body lumen, it also importantto design stents that may be easily removed and/or re-positioned fromthe body lumen post-deployment. Stents including bare portions (i.e.,uncovered portions) designed to promote tissue ingrowth (e.g., to reducestent migration as described above) may also be more difficult to removeonce the tissue has anchored the stent in the body lumen. One method toreduce the force necessary to remove a stent from a body lumen mayinclude positioning a covered, expandable secondary stent within thelumen of the primary (e.g., anchoring) stent. The radial expansion ofthe secondary stent within the lumen of the primary stent may cause thetissue ingrowth to recede, thereby reducing the force necessary toremove both the primary and secondary stents from the wall of the bodylumen. Examples of secondary medical devices which are capable of beingutilized with other medical devices are disclosed herein.

FIG. 1 shows an example stent 10. Stent 10 may have a first end 21, asecond end 23 and a lumen extending therein. When positioned in a bodylumen (e.g., esophagus) first or proximal end 21 may be defined as theend of stent 10 closest to a patient's mouth and second or distal end 23may be defined as the end of stent 10 closest to a patient's stomach.

Additionally, stent 10 may include one or more stent strut members 12forming a tubular scaffold. Stent strut members 12 may extend helically,longitudinally, circumferentially, or otherwise along stent 10. WhileFIG. 1 shows stent strut members 12 extending along the entire length ofstent 10, in other examples, the stent strut members 12 may extend onlyalong a portion of stent 10.

Additionally, FIG. 1 shows example stent 10 including a first flared endregion 14 proximate the first end 21 and/or a second flared region 16proximate the second end 23 of stent 10. In some instances, first flaredregion 14 and second flared region 16 may be defined as an increase inthe outer diameter, the inner diameter or both the inner and outerdiameter along one or both of the first end 21 and/or second end 23 ofstent 10. Further, FIG. 1 illustrates stent 10 including a medial region18 positioned between first flared region 14 and second flared region16.

However, it is contemplated that while FIG. 1 shows stent 10 includingboth a first flared region 14 and a second flared region 16, stent 10may only include one flared region. For example, it is contemplated thatstent 10 may include only flared region 14 or flared region 16. It isfurther contemplated that all or a portion of first flared region 14and/or second flared region 16 may flare outwardly (e.g., away from thecentral, longitudinal axis of stent 10). Alternatively, it is furthercontemplated that all or a portion of first flared region 14 and/orsecond flared region 16 may flare inwardly (e.g., toward the central,longitudinal axis of stent 10).

In some instances, stent 10 may be a self-expanding stent or stent 10may be a balloon expandable stent. Self-expanding stent examples mayinclude stents having one or more struts 12 combined to form a rigidand/or semi-rigid stent structure. For example, stent struts 12 may bewires or filaments which are braided, wrapped, intertwined, interwoven,weaved, knitted, looped (e.g., bobbinet-style) or the like to form thestent structure. For example, while the example stents disclosed hereinmay resemble a braided stent, this is not intended to limit the possiblestent configurations. Rather, the stents depicted in the Figures may bestents that are knitted, braided, wrapped, intertwined, interwoven,weaved, looped (e.g., bobbinet-style) or the like to form the stentstructure. Alternatively, stent 10 may be a monolithic structure formedfrom a cylindrical tubular member, such as a single, cylindrical tubularlaser-cut Nitinol tubular member, in which the remaining portions of thetubular member form the stent struts 12. Openings or interstices throughthe wall of the stent 10 may be defined between adjacent stent struts12.

Stent 10 in examples disclosed herein may be constructed from a varietyof materials. For example, stent 10 (e.g., self-expanding or balloonexpandable) may be constructed from a metal (e.g., Nitinol, Elgiloy,etc.). In other instances, stent 10 may be constructed from a polymericmaterial (e.g., PET). In yet other instances, stent 10 may beconstructed from a combination of metallic and polymeric materials.Additionally, stent 10 may include a bioabsorbable and/or biodegradablematerial.

In some instances, example stent 10 may include one or more layerspositioned on and/or adjacent to the inner and/or outer surface of thetubular scaffold of stent 10. For example, FIG. 1 shows example stent 10including an outer layer 22 (depicted as a dotted pattern in FIG. 1)disposed along a portion of the outer surface of stent 10 (e.g., alongthe first flared portion 14 and/or the second flared portion 16 of stent10). In some instances, outer layer 22 may be an elastomeric ornon-elastomeric material. For example, outer layer 22 may be a polymericmaterial, such as silicone, polyurethane, or the like.

Additionally, example stent 10 may include one or more layers positionedon and/or adjacent to the inner surface of stent 10. While not shown inFIG. 1 (but shown in FIG. 2), stent 10 may include an inner layer 20disposed within the lumen of stent 10. In some instances, inner layer 20may be an elastomeric or non-elastomeric material. For example, innerlayer 20 may be a polymeric material, such as silicone, polyurethane,UE, PVDF, Chronoflex® or similar biocompatible polymeric formulations.

It can be appreciated that as inner layer 20 and outer layer 22 extendoutwardly and inwardly, respectively, they may touch and/or form aninterface region within the spaces (e.g., openings, cells, interstices)in the wall of tubular scaffolding of stent 10. Further, the inner layer20 and outer layer 22 may additionally extend between adjacent struts12, thereby filling any space between adjacent strut members 12 of thetubular scaffold. Stent 10 may include areas in which one or morefilaments 12 are surrounded, encased and/or covered by the outer layer22 and/or inner layer 20. For example, some portions of stent 10 mayinclude filaments 12 which are sandwiched between outer layer 22 andinner layer 20.

FIG. 2 shows a cross-section of example stent 10 along line 2-2 ofFIG. 1. FIG. 2 illustrates that first flared region 14 and/or secondflared region 16 may include tapered portion 25 and end portion 27.While FIG. 2 shows tapered portions tapering radially outward towardends of stent 10, it is contemplated that one or more of taperedportions 25 may, alternatively, taper radially inward.

FIG. 2 further illustrates inner layer 20 extending along all or aportion of the inner surface 24 of stent 10. For example, FIG. 2illustrates inner layer 20 extending along an inner surface of endportions 27, tapered portions 25 and medial portion 18. For purposes ofthe discussion herein, inner layer 20 may be interchangeably referred toas a liner, coating and/or covering. Liner 20 may extendcircumferentially around the lumen of stent member 10. In other words,it can be appreciated that liner 20 may be defined as an annular layerthat extends continuously around the lumen of stent member 10. Further,liner 20 may extend continuously (e.g., uninterrupted) around the lumenof stent 10, from the first end 21 to the second end 23.

As discussed above, FIG. 2 illustrates stent 10 may include an outerlayer 22 disposed along an outer surface 26 of stent 10. For example, insome instances, stent 10 may include an outer layer 22 disposed alongthe outer surface of one or more of end portions 27.

In some instances (such as that illustrated in FIG. 2), outer layer 22may be a continuous extension of inner layer 20. For example, FIG. 2shows inner layer 20 extending along the inner surface 24 of endportions 27, whereby inner layer 20 “wraps” over the end 28 of the endportion 27 and continues to extend along the outer surface of endportion 27. It should be noted that, in this example, what has beendescribed above as outer layer 22 may define the portion of the innerlayer 20 which has “wrapped over” end 28 of tubular scaffold of stent 10and further extends along the outer surface of end portion 27. Further,both the inner layer 20, and the portion of the inner layer 20 thatwraps over end 28 of stent 10 to form outer layer 22 may, together,sandwich filaments 12 therebetween. Further, while FIG. 2 illustratesinner layer 20 wrapping around (e.g., extending continuously around)both end portions 27 of stent 10 in FIG. 2, it is contemplated thatinner layer 20 may wrap around only one end portion 27 of stent member10.

FIG. 2 illustrates that inner layer 20 may be fixedly attached to theinner surface of end portions 27 and/or tapered regions 25. In otherwords, FIG. 2 shows that inner layer 20 may be adhered (e.g., affixed,secured, etc.) to the inner surface of strut members 12 which define endportions 27 and/or tapered regions 25 of stent 10.

Additionally, FIG. 2 illustrates that, in some examples, a portion ofinner layer 20 may be spaced away from (i.e., spaced radially inward of)the inner surface 24 of stent 10, providing a gap or space therebetween.In particular, FIG. 2 illustrates that the portion of inner layer 20extending along the medial portion 18 of stent member 10 may beunattached to medial portion 18 of the tubular scaffold of stent 10 andspaced radially inward from the inner surface 24 of the tubular scaffoldof stent 10. For example, FIG. 2 shows that liner 20 may be attached(e.g., circumferentially) at a first attachment point 30 and a secondattachment point 32, with the length of liner 20 between attachmentpoints 30/32 remaining unattached (i.e., not directly attached) to thetubular scaffold of medial portion 18 of stent 10. FIG. 2 shows thatinner layer 20 may be unattached to the inner surface 24 of the tubularscaffold (i.e., the struts 12) of stent 10 along a portion of stent 10between first attachment point 30 and second attachment point 32. Itshould be noted that the portion of stent 10 shown in FIG. 2 in whichinner layer 20 is unattached to the inner surface 24 of struts 12 ofstent 10 may correspond to the medial portion 18 of stent 10 describedabove. In other words, in some examples, inner layer 20 may beunattached and thereby extend radially inward from the inner surface 24of the tubular scaffold (i.e., struts 12) along the medial portion 18 ofstent 10.

As discussed above, stents that are designed to be positioned in a bodylumen (e.g., esophageal or gastrointestinal tract) may have a tendencyto migrate (due to peristalsis and/or the generally moist and inherentlylubricious environment of the body lumens). Therefore, one method toreduce stent migration may include exposing tissue ingrowth promotingregions, such as uncovered and/or bare metal portions of the stent tothe tissue of the body lumen. The uncovered or bare stent scaffold mayprovide a structure that promotes tissue ingrowth into the intersticesor openings thereof. The tissue ingrowth may anchor the stent in placeand reduce the risk of stent migration.

Accordingly, it can be appreciated that the portions of stent 10discussed above which include an inner and/or outer layer which isattached (e.g., covers) stent struts or filaments 12 may act to preventtissue from growing into the interstices or openings thereof. Forexample, the struts or filaments 12 of tapered regions 25 and endportions 27 of stent 10 which include inner layer 20 and/or outer layer22 attached thereto to thereby span across interstices of the tubularscaffold may prevent tissue ingrowth along their respective surfaces andinterstices therebetween.

However, it can be appreciated that tissue may be permitted to growaround, between, through, within, etc. those filaments 12 of stent 10 inwhich inner layer 20 is not attached (e.g., the portion of inner layer20 extending along medial portion 18 of stent 10). In other words, FIG.2 illustrates a “tissue ingrowth region” 36 defined along medial region18 of stent 10. The detailed view of FIG. 2 illustrates that tissueingrowth region 36 may be extend radially inward from the inner surface24 of stent member 10 to the outer surface 38 of inner liner 20. Thedistance between the inner surface 24 of stent member 10 to the outersurface 38 of inner liner 20 may be depicted as “D₁” in FIG. 2. Distance“D₁” may be about 0.5 mm-10 mm, or about 1 mm-6 mm, or about 1.5 mm-4mm, or about 2 mm.

FIG. 2 further illustrates that tissue ingrowth region 36 may be definedas the space between the inner surface 24 of the tubular scaffold ofstent 10 and the outer surface 38 of liner 20 extending betweenattachment points 30/32. Tissue ingrowth region 36 may be positionedbetween attachment points 30/32. Thus, tissue ingrowth region 36 may bedefined as a space between the inner surface 24 of the tubular walldefined by struts or filaments 12 of the stent 10 and the outer surface38 of the wall of the inner layer 20 between the circumferentialattachment points 30/32. Further, tissue ingrowth region 36 may bedefined as extending circumferentially within the lumen of the tubularscaffold of stent 10. In other words, it can be appreciated that tissueingrowth region 36 may be defined as an annular space that extendscontinuously around the lumen of the tubular scaffold formed by strutsor filaments of stent 10 radially inward of the stent wall.

It can further be appreciated that liner 20 may be constructed from anelastic material in some instances. Accordingly, a liner 20 including anelastic material component may be able to stretch radially inward. Forexample, as tissue grows through the interstices of stent member 10, itmay push radially inward against the outer surface 38 of inner layer 20.In response, inner layer 20 may deflect, stretch, etc. radially inwardin response to inward forces (e.g., tissue ingrowth) acting thereupon.In particular, the space D₁ between the inner surface 24 of stent 10 andthe outer surface 38 of liner 20 may increase as the liner 20 deflectsradially inward. In other embodiments, the liner 20 may be inelasticand, therefore, may not deflect relative to stent 10.

While liner 20 may include an elastic element permitting it to deflectradially inward from the inner surface 24 of the tubular scaffold ofstent 10, in some instances it may be desirable to limit the amount ofdeflection of inner layer 20. For example, FIG. 2 illustrates that innerlayer 20 defines a lumen 40 extending therein. Lumen 40 may be designedto permit food and/or or other digestible material to flow therethrough.Therefore, in some instances it may be desirable to design inner layer20 to preserve the passageway defined by lumen 40 to permit food and/orother digestible material to flow through stent 10 when implanted in abody lumen. In other words, it may be desirable in some instances toprevent lumen 40 from closing radially inward in on itself. In someinstances the inner layer 20 may include reinforcing filaments (e.g.,fibers) embedded in the material of the inner layer 20 that may be drawntaut after a threshold amount of stretching of the material of the innerlayer 20 to prevent further stretching of the inner layer 20. In someinstances, the reinforcement filaments may be arranged longitudinally,circumferentially, helically, randomly, or otherwise arranged in theinner layer 20.

FIG. 2 depicts an inner diameter of tubular scaffold of stent 10 alongmedial region 18 as “D₄.” Further, FIG. 2 depicts an inner diameter ofinner liner 20 along medial region 18 as “D₂.” Diameter “D₄” may beabout 10 mm-30 mm, or about 15 mm-25 mm, or about 20 mm, in someinstances. Further, diameter “D₂” may be about 10 mm-30 mm, or about 15mm-25 mm, or about 18 mm, in some instances. Additionally, in someinstances, it may be desirable to design inner liner 20 such that thediameter “D₂” is greater than or equal to a given percentage of diameter“D₄.” For example, in some instances diameter “D₂” may be greater thanor equal to 10% of “D₄”, or greater than or equal to 25% of “D₄”, orgreater than or equal to 50% of “D₄”, or greater than or equal to 60% of“D₄”, or greater than or equal to 75% of “D₄”, or “D₂” may be between10-20% of “D₄”, or “D₂” may be between 20-30% of “D₄”, or “D₂” may bebetween 30-40% of “D₄”, or “D₂” may be between 40-50% of “D₄”, or “D₂”may be between 50-75% of “D₄”, or “D₂” may be between 75%-90% of “D₄”,in some instances.

It can be appreciated that limiting the amount of deflection of innerliner 20 may not only assure that lumen 40 remains open, but it alsolimits that amount of tissue ingrowth occurring along stent 10. Forexample, by limiting the degree to which liner 20 may deflect radiallyinward along medial region 18, the amount of tissue ingrowth occurringalong medial 18 may be controlled. As discussed above, controlling theamount of tissue ingrowth occurring along stent 10 may be desirablebecause the amount of tissue ingrowth may directly correspond to theforce necessary to remove stent 10 from a body lumen. In other words,the stent 10 maybe customized to have a given removal force by limitingthe amount of elasticity (e.g., and thereby limiting the amount ofradially inward deflection) of liner 20.

As can be appreciated from FIG. 2, end portions 27 may include an innerdiameter depicted as “D₃.” Diameter “D₃” may be greater than or equal todiameter “D₂.” Diameter “D₃” may be about 15 mm-35 mm, or about 20 mm-30mm, or about 25 mm, in some instances. In other words, inner layer 20may be generally shaped to taper longitudinally from the end portion 27closest to first end 21 to the medial portion 18. For example, thetapered portion 25 may bear some resemblance to a cone-shaped funnel.Further, as illustrated in FIG. 2, stent 10 may taper inwardly towardcentral longitudinal axis of stent 10 along flared portion 14 and maytaper outwardly away from the central longitudinal axis of stent 10along flared portion 16.

FIG. 3 illustrates a cross-section along line 3-3 of FIG. 2. Asdescribed above, this cross-section is taken through end portion 27 offlared region 14. As illustrated in FIG. 3, the filaments 12 of stent 10defining end portion 27 may be sandwiched between inner layer 20 andouter layer 22. In other words, FIG. 3 illustrates that some portions ofstent 10 (e.g., along flared region 14 and/or flared region 16),filaments 12 may have both inner layer 20 and outer layer 22 directlyattached thereto. In other words, along some portions of stent 10 (e.g.,along flared region 14 and/or flared region 16) no space may existbetween filaments 12 and both inner layer 20 and outer layer 22.

FIG. 4 illustrates a cross-section along line 4-4 of FIG. 2. Asdescribed above, this cross-section is taken through medial portion 18of stent 10. As illustrated in FIG. 4, the inner layer 20 of stent 10may be spaced away from (i.e., radially inward of) filaments 12 of stent10 along medial portion 18. Further, FIG. 4 illustrates tissue ingrowthregion 36 extending between the inner surface 24 of filaments 12 ofstent 10 and the outwardly-facing surface 38 of inner member 20.Additionally, FIG. 4 illustrates tissue ingrowth region 36 extendingcircumferentially around the longitudinal axis of stent 10 radiallyoutward of liner 20 and radially inward of filaments 12 of the tubularscaffold.

While the above discussion disclosed examples in which inner layer 20and outer layer 22 are fixedly attached (e.g., directly secured) to theend portions 27 and/or tapered portions 25, other configurations arecontemplated. For example, FIG. 5 illustrates an example stent member110. Stent 110 may be similar in form and functionality to stent 10described above. For example, stent 110 may include a liner 120 disposedwithin a lumen of the tubular scaffold of stent 110. Further, asillustrated in FIG. 5, liner 120 may be circumferentially attached alongthe inner surface 124 of stent 110 at attachment point 130 and/orattachment point 132. Attachment points 130/132 may be located atopposing end regions of stent 110, such as in opposing flared endregions of stent 110.

However, FIG. 5 illustrates that different attachment point locations130/132 are contemplated along stent member 110. For simplicitypurposes, example positions contemplated for attachment points 130/132are depicted in terms of a distance from the end 128 of stent member110. For example, the attachment points 130/132 are depicted as being adistance “W” (as measured along the outer surface 126 of stent 110) fromend 128. In other examples, attachment points 130/132 may be positionedat distances depicted as “X,” “Y” and “Z” (as measured longitudinallyfrom end 128 of stent 110. Distance “Z” may be understood to be theequivalent attachment location of attachment points 30/32 along stent110 described above. Additionally, in some examples distance “W” may beapproximately 25% of distance “Z,” distance “X” may be approximately 50%of distance “Z” and distance “Y” may be approximately 75% of distance“Z.”

Additionally, it is contemplated that liner 120 may not be attachedalong the inner surface 124 of stent 110. For example, attachment points130/132 may be located at the end point 128 of stent 110. Further, ininstances where attachment points 130/132 are located at ends 128, liner120 may cover and or encapsulate the ends 128 of stent 110.

It can be appreciated from FIG. 5 that the different attachment point130/132 along stent 110 may correspond to different size tissue ingrowthregions 136(described above as tissue ingrowth region 36 of stent 10).For example, the tissue ingrowth section 136 defined by attachment point130/132 located a distance “W” from end 128 may be larger than a tissueingrowth region 136 defined by attachment point 130/132 located adistance “Y” from end 128. For reasons discussed above, it can beappreciated that the larger tissue ingrowth regions may create a stent110 which has increased removal forces.

Outer layer 122 may also extend any desired distance from end 128 ofstent 110 along the outer surface of the tubular scaffold defined byfilaments or struts 112. For example, outer layer 122 may extend adistance depicted as “W,” “X,” “Y” or “Z” from end 128. The distanceouter layer 122 extends from end 128 of stent 110 may be the same ordifferent than the distance for attachment points 130/132.

While the above discussion of stent 10 and stent 110 illustrates avariety of attachment locations along stent 10, it is contemplated thatliner 20 may be attached at any location along the inner surface 24and/or outer surface of stent member 10. The different attachmentlocations may result in stents having different performancecharacteristics (e.g., different removal forces, differentanti-migration properties). It is noted that the attachment distancesshown in FIG. 5 are equally applicable to the attachment point 132 atthe opposite end of stent 110 and/or outer layer 122 at the opposite endof stent 110.

FIGS. 6A-8B illustrate example stents that may be similar in form andfunction to the stent designs disclosed above. For example, each of thestents shown in FIGS. 6A-8B may include an inner liner disposed withinthe lumen of the tubular scaffold of stent (e.g., as shown in FIG. 2).Further, each of the stents shown in FIGS. 6A-8B may also include anouter layer as described above (e.g., as shown in FIG. 1) extendingalong at least a portion of the flared end regions of the tubularscaffold. However, the stents illustrated in FIGS. 6A-8B may furtherinclude an additional outer layer (which could be formed separately orin conjunction with the outer layer disposed on the flared end regionsand/or the inner layer) disposed along the outer surface of the medialportion of the stent, leaving a remainder of the tubular scaffolduncovered to promote tissue ingrowth therethrough.

For example, FIG. 6A shows an example stent 210. Example stent 210 thatmay be similar in form and function to the stent designs disclosedabove. However, as FIG. 6A illustrates, stent 210 includes additionalouter layers 223 disposed along the outer surface 226 of the tubularscaffold of stent 210. FIG. 6A shows outer layers 223 as circumferentialrings of material which may be positioned such that they extendcircumferentially around the outer surface 226 of stent 210 (the dashedlines in FIG. 6A depict the outer layers 223 extending circumferentiallyaround the outer surface 226 of stent 210) and spaced apart relative toone another. In some examples, outer layers 223 may be oriented suchthat they extend laterally across stent 210. As shown in FIG. 6A,individual outer layers 223 may be spaced longitudinally apart from oneanother. It can be appreciated that the configuration of outer layers223 creates one or more tissue ingrowth regions 236 (similar to infunction to those described above) along the medial region of stent 210.Tissue ingrowth regions 236 may be circumferentially uncovered portionsof the tubular scaffold of stent 210. Inner layer 220 may be locatedradially inward of tissue ingrowth regions 236 to limit the amount atissue ingrowth permitted.

Alternatively, some stent examples disclosed herein may be designed suchthat one or more portions of an inner layer extending along the innersurface of the stent may be spaced away from (i.e., spaced radiallyinward of) the inner surface of the stent, providing a gap or spacetherebetween. For example, FIG. 6B (which may be similar in form andfunction to the stent design disclosed above with respect to FIG. 6A)illustrates an alternative example stent having one or more portions ofinner layer 220 extending along the inner surface 224 of stent 210 maybe unattached to the inner surface of stent 210 and spaced radiallyinward from the inner surface 224 of the tubular stent 210 while otherportions of the inner layer 220 are attached to the inner surface 224 ofstent 210. The space created by the inner layer 220 extending radiallyinward of the inner surface 224 of the stent 210 may define one or moretissue ingrowth regions 238. Tissue ingrowth regions 238 may extendcircumferentially around the inner surface 224 of stent 210.

FIG. 7 shows another example stent 310. Example stent 310 may be similarin form and function to the stent designs disclosed above. However, asFIG. 7 illustrates, stent 310 includes additional outer layer 323disposed along the outer surface 326 of the tubular scaffold of stent310. FIG. 7 shows outer layer 323 may be positioned such that it extendscircumferentially around the outer surface 326 of stent 310 (the dashedlines in FIG. 7 depict outer layer 323 extending circumferentiallyaround the outer surface 326 of stent 310). However, FIG. 7 shows thatouter layer 323 may be oriented such it extends in a helicalconfiguration around the outer surface 326 of stent 310. It can beappreciated that the configuration of outer layer 323 creates one ormore tissue ingrowth regions 336 (similar in form and function to thosedescribed above) along stent 310. Tissue ingrowth regions 336 may becircumferentially uncovered portions of the tubular scaffold of stent310. Inner layer 320 may be located radially inward of tissue ingrowthregions 336 to limit the amount a tissue ingrowth permitted.

Alternatively, some stent examples disclosed herein may be designed suchthat one or more portions of an inner layer extending along the innersurface of the stent may be spaced away from (i.e., spaced radiallyinward of) the inner surface of the stent, providing a gap or spacetherebetween. For example, FIG. 7B (which may be similar in form andfunction to the stent design disclosed above with respect to FIG. 7A)illustrates an alternative stent example having one or more portions ofinner layer 320 may extend in a helical orientation along and attachedto the inner surface 324 of stent 310. It can be appreciated that thehelical configuration of inner layer 320 creates one or more tissueingrowth regions 338 (similar in form and function to those describedabove) along stent 310. Tissue ingrowth regions 338 may be helicallyoriented uncovered portions of the tubular scaffold of stent 310.

FIG. 8A shows an example stent 410. Example stent 410 that may besimilar in form and function to the stent designs disclosed above.However, as FIG. 8A illustrates, stent 410 includes additional outerlayers 423 disposed along the outer surface 426 of stent 410. FIG. 8Ashows outer layers 423 may be positioned such that they extendlongitudinally along the outer surface 426 of stent 410. As shown inFIG. 8A, individual outer layers 423 may be circumferentially spacedapart from one another. It can be appreciated that the configuration ofouter layers 423 creates one or more tissue ingrowth regions 436(similar to in function to those described above) along the stent 410.Tissue ingrowth regions 436 may be uncovered portions of the tubularscaffold of stent 410. Inner layer 420 may be located radially inward oftissue ingrowth regions 436 to limit the amount a tissue ingrowthpermitted.

Alternatively, some stent examples disclosed herein may be designed suchthat one or more portions of an inner layer extending along the innersurface of the stent may be spaced away from (i.e., spaced radiallyinward of) the inner surface of the stent, providing a gap or spacetherebetween. FIG. 8B illustrates an alternative stent example (whichmay be similar in form and function to the stent design disclosed abovewith respect to FIG. 8A) having an inner layer 420 spaced away from aninner surface of stent 410. As shown in FIG. 8B and FIG. 8C (discussedbelow), inner layer 420 may include one or more discrete attachmentpoints 425 along the inner surface of stent 410 in which the inner layer420 is attached to the inner surface of stent 410. It should be notedthat the discrete attachment points of inner layer 420 may extend thefull (or partial) longitudinal length (e.g., from the distal end regionto the proximal end region) along the inner surface of stent 410.

FIG. 8C illustrates an example cross-section along line 8C-8C of examplestent 410 shown in FIG. 8B. FIG. 8C illustrates that one or moreportions of inner layer 420 may be attached along the inner surface ofstent 410. Further, the inner layer 420 may be attached along the innersurface of stent 410 at one or more discrete attachment points 425. Itcan be appreciated that the space between the discrete attachment points425 may create one or more tissue ingrowth regions 436.

Example stents disclosed herein may include one or more anchoringmembers designed to prevent the tubular member from shifting withrespect to a body lumen in which the stent member is implanted. Forexample, some stents disclosed herein may include anti-migrationelements. Anti-migration elements may include hooks, barbs, posts,flares, hoops, fins, quills, tines or the like. Anti-migration featuresmay be beneficial in controlling the amount that a stent moves duringand/or after deployment in the body lumen.

As discussed above, while medical device 10 is implanted along a bodylumen, tissue ingrowth may occur along the tissue ingrowth region, whichmay reduce migration of implantable medical device 10 within the bodylumen. However, in some examples, it may be necessary to remove medicaldevice 10 from the body lumen. In at least some examples contemplatedherein, removal of medical device 10 (which is effectively anchored tothe body lumen via tissue ingrowth) may include positioning a secondmedical device (e.g., a second expandable stent) within the lumen of themedical device 10 such the second medical device may exert a radiallyoutward force along the tissue ingrowth region, thereby causing theingrown tissue to recede. In other words, a second expandable stent maybe deployed within the lumen of medical device 10, whereby the radialoutward expansion of the second stent “pushes back” the ingrown tissue,causing it to recede radially outward (toward the vessel wall) andthereby reducing the force necessary to remove medical device 10 and/orthe second stent. This method of using a second medical device to removemedical device 10 (e.g., the anchored stent) will be further illustratedand described below.

FIG. 9 shows an example second stent 510. In some instances, secondstent 510 may be referred to as an interior stent, removal stent and/orretrieval stent 510 configured to by positioned within a lumen of apreviously implanted stent. Stent 510 may have a first end 521, anopposite second end 523 and a lumen extending therein. When positionedin a body lumen (e.g., esophagus) the first or proximal end 521 may bedefined as the end of stent 510 closest to a patient's mouth and thesecond or distal end 523 may be defined as the end of stent 510 closestto a patient's stomach.

Additionally, stent 510 may include one or more stent strut members 512forming a tubular scaffold. Stent strut members 512 may extendhelically, longitudinally, circumferentially, or otherwise along stent510. While FIG. 9 shows stent strut members 512 extending along theentire length of stent 510, in other examples, the stent strut members512 may extend only along a portion of stent 510. In some instances,stent struts 512 may be wires or filaments which are braided, wrapped,intertwined, interwoven, weaved, knitted, loops (e.g., bobbinet-style)or the like to form the stent structure. In other instances, the stentstruts 512 may be portions of a monolithic structure formed from acylindrical tubular member, such as a laser-cut Nitinol tube.

Additionally, FIG. 9 shows example stent 510 including a first flaredend region 514 proximate the first end 521 and/or a second flared endregion 516 proximate the second end 523 of stent 510. In some instances,first flared region 514 and second flared region 516 may be defined asan increase in the outer diameter, the inner diameter or both the innerand outer diameters along one or both of the first end 521 and/or secondend 523 of stent 510. Further, FIG. 9 illustrates stent 510 including amedial region 518 positioned between first flared region 514 and secondflared region 516.

However, it is contemplated that while FIG. 9 shows stent 510 includingboth a first flared region 514 and a second flared region 516, stent 510may only include one flared region. For example, it is contemplated thatstent 510 may include only flared region 514 or flared region 516. It isfurther contemplated that all or a portion of first flared region 514and/or second flared region 516 may flare outwardly (e.g., away from thecentral, longitudinal axis of stent 510). Alternatively, it is furthercontemplated that all or a portion of first flared region 514 and/orsecond flared region 516 may flare inwardly (e.g., toward the central,longitudinal axis of stent 510).

In some instances, stent 510 may be a self-expanding stent or stent 510may be a balloon expandable stent. Self-expanding stent examples mayinclude stents having one or more struts 512 combined to form a rigidand/or semi-rigid stent structure. For example, stent struts 512 may bewires or filaments which are braided, wrapped, intertwined, interwoven,weaved, knitted, looped (e.g., bobbinet-style) and combinations thereofto form the stent structure. For example, while the example stentsdisclosed herein may resemble a braided stent, this is not intended tolimit the possible stent configurations. Rather, the stents depicted inthe Figures may be stents that are knitted, braided, wrapped,intertwined, interwoven, weaved, looped (e.g., bobbinet-style) or thelike to form the stent structure. Alternatively, stent 510 may be amonolithic structure formed from a cylindrical tubular member, such as asingle, cylindrical tubular laser-cut Nitinol tubular member, in whichthe remaining portions of the tubular member form the stent struts 512.Openings or interstices through the wall of the stent 510 may be definedbetween adjacent stent struts 512.

Stent 510 in examples disclosed herein may be constructed from a varietyof materials. For example, stent 510 (e.g., self-expanding or balloonexpandable) may be constructed from a metal (e.g., Nitinol, Elgiloy,etc.). In other instances, stent 510 may be constructed from a polymericmaterial (e.g., PET). In yet other instances, stent 510 may beconstructed from a combination of metallic and polymeric materials.Additionally, stent 510 may include a bioabsorbable and/or biodegradablematerial.

In some instances, example stent 510 may include one or more layers(e.g., coverings) positioned on and/or adjacent to the inner and/orouter surface of the tubular scaffold of stent 510. For example, FIG. 9shows example stent 510 including an outer layer 522 (depicted as adotted pattern in FIG. 9) disposed along at least a portion of the outersurface of stent 510 (e.g., along the middle portion, along the firstflared portion 514 and/or the second flared portion 516 of stent 510).In some instances, the outer layer 522 may cover the entire outersurface of the tubular scaffold of stent 510. In some instances, outerlayer 522 may be an elastomeric or non-elastomeric material. Forexample, outer layer 522 may be a polymeric material, such as silicone,polyurethane, or the like.

Additionally, example stent 510 may include one or more layerspositioned on and/or adjacent to the inner surface of stent 510. Forexample, stent 510 may include an inner layer (not shown in the Figures)disposed within the lumen of stent 510. In some instances, inner layermay be an elastomeric or non-elastomeric material. For example, innerlayer may be a polymeric material, such as silicone, polyurethane, UE,PVDF, Chronoflex® or similar biocompatible polymeric formulations.

FIG. 10 shows a cross-section of example stent 510 along line 10-10 ofFIG. 9. FIG. 10 illustrates that first flared region 514 and/or secondflared region 516 may include tapered portion 525 and end portion 527.While FIG. 10 shows tapered portions tapering radially outward towardends of stent 510, it is contemplated that one or more of taperedportions 525 may, alternatively, taper radially inward.

As discussed above, FIG. 10 illustrates stent 510 may include an outerlayer 522 disposed along an outer surface of stent 510. For example, insome instances, stent 510 may include an outer layer 522 disposed alongthe outer surface of a middle portion between flared ends 514, 516, oneor more of both tapered portions 525 and/or end portions 527. Further,in some examples, outer layer 522 may extend longitudinally along theentire length and circumferentially around the entire circumference ofouter surface of stent 510.

As will be discussed in greater detail below, FIGS. 11-13 illustrate anexample stent 10 undergoing a hyperplastic response, FIGS. 14-17illustrate the deployment and positioning of an example retrieval stentwithin stent 10 and FIG. 18 illustrates the removal of both stent 10 andthe retrieval stent 510.

FIGS. 11-13 illustrate an example stent undergoing a hyperplasticresponse of tissue within an example body lumen subsequent toimplantation of stent 10 within a body lumen 11. FIG. 11 shows examplestent 10 deployed in body lumen 11. As illustrated, upon initialdeployment in the body lumen 11, the end portion 27 of the first flaredregion 14 and the end portion 27 of the second flared region 16 mayapply a radially outward force upon the inner surface of body lumen 11as the expandable scaffold of stent 10 expands to an expanded state inthe body lumen 11. This radially outward force exerted on the innersurface of body lumen 11 may provide a temporary resistance to migrationof stent 10 within the body lumen 11.

Additionally, the end portions 27 of stent 10 may contact the tissue onthe inner surface of body lumen 11. This contact of the end portions 27with the tissue of the inner surface of the body lumen 11 may provide aseal that funnels food or other material through lumen 40 of stent 10.For example, as food or other material travels down the esophagus, theflared portions 14/16 of stent 10 may prevent the food from travelingalong the exterior of stent 10 and along the inner surface of body lumen11. Rather, flared portions 14/16 are designed to provide acircumferential seal around the inner surface of body lumen 11 such thatthe food is directed through the lumen 40 of stent 10. As discussedabove, the inner layer 20 of stent 10 may create a passageway (e.g.,lumen 40) through which food and other material may travel (withoutleaking to the outer surface of stent 10).

Over time, tissue may grow through interstices of the stent scaffoldalong medical region 18. FIG. 12 illustrates tissue 13 extending throughinterstices of the stent filaments 12 along the medial region 18 ofstent member 10 radially inward of the uncovered portion of the tubularscaffold of stent 10. FIG. 12 further illustrates that the tissue 13 isgrowing into the tissue ingrowth region 36 toward liner 20 (as depictedby the arrows in FIG. 12). Thus, tissue may grow through interstices ofthe tubular scaffold of stent 10 and around struts or filaments 12 oftubular scaffold of stent 10 throughout the uncovered portion of medialregion 18.

Inner layer 20 may limit the amount of tissue in-growth permitted. FIG.13 illustrates that tissue 13 has grown radially inward from the wall ofexample body lumen 11 to a position in which it has contacted innerlayer 20 radially inward. However, as shown in FIG. 13, inner layer 20has reached a point at which it will no longer deflect radially inward,and therefore prevents tissue 13 from further collapsing lumen 40 ofstent member 10 (as depicted by the double-ended arrow in FIG. 13).Thus, inner layer 20 may be configured to maintain a desired lumendiameter through stent 10 while stent 10 is implanted in a patient.

In some instances, it may be desirable to remove stent 10 subsequenttissue in-growth through interstices of the tubular scaffold. However,the tissue-ingrowth may hinder removal and/or cause undesirable traumato the body lumen. As discussed above, FIGS. 14-18 illustrate an examplemethodology for retrieving and/or removing an example stent 10 (or anyother devices disclosed herein) from a body lumen (e.g., the esophagus)while reducing the amount of trauma to the body lumen. Example stent 10shown in FIGS. 14-18 may depict stent 10 illustrated and described withrespect to FIGS. 11-13. However, stent 10 described in the followingmethodology may also be similar in form and function to stent 10 ofFIGS. 1 and 2 discussed above. Further, while the following figuresdescribe example stent 10 being retrieved and/or removed from theesophagus, it is contemplated that the methodology may be used toretrieve and/or remove stent 10 (or any other devices disclosed herein)from any other body lumen.

FIG. 14 shows an example first step in removing stent 10 from body lumen11. Specifically, delivery device 50 may be advanced through body lumen11 to a first end 21 of stent 10. The end portion 52 of delivery device50 may then be further advanced through the lumen 40 of the stent 10such that the end portion 52 is positioned adjacent the second end 23 ofthe stent 10.

FIG. 15 illustrates an example second step in removing stent 10 frombody lumen 11. Specifically, FIG. 15 illustrates that a clinician mayretract the end portion 52 of the delivery device 50 in a proximaldirection depicted by the arrow in FIG. 15. Specifically, the deliverydevice 50 (e.g., an outer sheath of delivery device 50) may be retractedin a distal-to-proximal direction within lumen 40 of the stent 10. Inother words, the delivery device may be retracted from second end 23toward the opposite end of the stent 10. FIG. 15 further illustratesthat as the delivery device 50 is retracted, the second end 523 ofsecondary stent 510 (e.g., retrieval stent) is deployed with the lumen40 of stent 10. Additionally, it can be appreciated that as retrievalstent 510 is deployed, it radially expands such that the outer covering522 of the second end 523 of stent 510 contacts the inner liner 20 ofstent 10. Further, as illustrated in FIG. 15, it may be desirable thatthe second end 523 of retrieval stent 510 and the second end 23 of stent10 be substantially aligned longitudinally along body lumen 11.

FIG. 16 illustrates an example third step in removing stent 10 from bodylumen 11. Specifically, FIG. 16 illustrates that delivery device 50 maybe fully retracted to a position in which retrieval stent 510 has beenfully deployed from the end portion 52 of the delivery device 50.Additionally, it can be appreciated that after retrieval stent 510 isfully deployed from delivery device 50, it expands radially outward suchthat the outer covering 522 of stent 510 contacts the inner liner 20 ofstent 10 throughout the length of stent 10, with the expandable scaffoldof stent 510 exerting a radially outward force on inner liner 20 ofstent 10. For example, the expandable scaffold of stent 510 can exert aradially outward force throughout the medial region 18 of the innerliner 20.

Further, as illustrated in FIG. 16, it may be desirable that the firstend 521 of retrieval stent 510 and the first end 21 of stent 10 may besubstantially aligned longitudinally along the body lumen 11. Further,FIG. 16 illustrates that in some instances it may be desirable that boththe first and second ends of retrieval stent 510 substantially alignwith the first and second ends of stent 10.

Additionally, it can be appreciated that in some instances the retrievalstent 510 may include a profile along its outer surface that matches theprofile of the inner surface of stent 10. In other words, in someinstances it may be desirable for stent 10 and retrieval stent 510 tohave a similar, or substantially equivalent geometric shape. It canfurther be appreciated that if the profile of retrieval stent 510matches the profile of stent 10, the retrieval stent 510, when deployedwithin the lumen 40 of stent 10, may contact substantially the entireinner surface of stent 10.

As discussed above, FIG. 16 further illustrates that when retrievalstent 510 is positioned and deployed within the lumen 40 of stent 10, itmay exert a radially outward force (depicted by the double-ended arrowsin FIG. 16) that pushes outward against the inner surface of stent 10.For, example, retrieval stent 510 may be configured to have a deployed,radially expanded outer diameter greater than the inner diameter of themedial region 18 of stent 10 to exert a radial outward force againstinner liner 20. Accordingly, this outward radial force may push theportion of liner 20 that is adjacent the tissue ingrowth region, therebyexerting an outward radial force against the tissue 13, as shown in FIG.16. It can be appreciated that stent 510 may be designed such that itexerts an outward radial force which is large enough to push both liner20 and tissue 13 radially outward toward body lumen 11, thereby causingtissue 13 to retreat and effectively die off. In some examples, theoutward radial force exerted by stent 510 may be about 0.10 N to about2.5 N, or about 0.15 N to about 2.0 N. In some instance, the outwardradial force exerted by stent 510 may be about 0.10 N or more, about0.15 N or more, about 0.5 N or more, about 1.0 N or more, about 1.5 N ormore, or about 2.0 N or more.

FIG. 17 illustrates stent 10 and retrieval stent 510 of FIG. 16 afterthe retrieval stent 510 has been deployed within stent 10 and allowed toexert an outward radial force along the tissue ingrowth region of liner20. As can appreciated from FIG. 17, the tissue 13 present in FIG. 16has effectively died off and liner 20 has relaxed to a position in whichit is positioned along the inner surface of the tubular scaffold ofstent 10 throughout medial region 18. As discussed above, because theretrieval stent 510 has reduced the amount of tissue 13 extendingthrough the stent struts 12 of stent 10, tissue 13 no longer attachesstent 10 to the inner surface of body lumen 11 with as much force aswhen the tissue 13 is fully ingrown into the stent struts 12.Accordingly, this reduced attachment force translates into a lower forcewhich is necessary to remove stent 10 and/or stent 510 from body lumen11.

FIG. 18 illustrates an example step in removing stent 10 from body lumen11. Removal of the stent 10 may be performed once tissue in-growth intothe interstices of the tubular scaffold of stent 10 has sufficientlyreceded. For example, removal of stent 10 may be performed approximately7-14 days after placing retrieval stent 510 within stent 10. In someinstances, removal of stent 10 may be performed within 1 week or less,within 2 weeks or less, or within 3 weeks or less after placingretrieval stent 510 within stent 10. Specifically, FIG. 18 illustratesthat a clinician may utilize a retrieval device 54 (e.g., forceps,clamp, etc.) to remove both stent 10 and/or retrieval stent 510. Asillustrated in FIG. 18, the retrieval device 54 map grasp the first endportions 21/521 of stent 10 and retrieval stent 510 and pull them in adirection out of the body (indicated by the arrow in FIG. 18). The forceexerted by the retrieval device 54 may be sufficient to remove both thestent 10 and retrieval stent 510 from the inner surface of the bodylumen 11 without damaging the inner surface of the body lumen 11.Alternatively, retrieval device 54 may grasp or hook a retrieval sutureextending circumferentially around the end of stent 10. When pulledproximally, the retrieval suture may collapse the proximal end of stent10 and/or the proximal end of stent 510 to facilitate withdrawal of thestents 10, 510. Accordingly, stents 10, 510 may be removed from the bodylumen 11 simultaneously. Alternatively, stents 10, 510 may be removedfrom the body lumen sequentially, if desired.

The materials that can be used for the various components of stent 10and stent 510 (and/or other stents disclosed herein) and the variousmedical devices disclosed herein may include those commonly associatedwith medical devices. For simplicity purposes, the following discussionmakes reference to stent 10 and stent 510 and other components of stent10 and stent 510. However, this is not intended to limit the devices andmethods described herein, as the discussion may be applied to othersimilar medical devices disclosed herein.

Stent 10 and stent 510 and other components of stent 10 and stent 510may be made from a metal, metal alloy, polymer (some examples of whichare disclosed below), a metal-polymer composite, ceramics, combinationsthereof, and the like, or other suitable material. Some examples ofsuitable polymers may include polytetrafluoroethylene (PTFE), ethylenetetrafluoroethylene (ETFE), fluorinated ethylene propylene (FEP),polyoxymethylene (POM, for example, DELRIN® available from DuPont),polyether block ester, polyurethane (for example, Polyurethane 85A),polypropylene (PP), polyvinylchloride (PVC), polyether-ester (forexample, ARNITEL® available from DSM Engineering Plastics), ether orester based copolymers (for example, butylene/poly(alkylene ether)phthalate and/or other polyester elastomers such as HYTREL® availablefrom DuPont), polyamide (for example, DURETHAN® available from Bayer orCRISTAMID® available from Elf Atochem), elastomeric polyamides, blockpolyamide/ethers, polyether block amide (PEBA, for example availableunder the trade name PEBAX®), ethylene vinyl acetate copolymers (EVA),silicones, polyethylene (PE), Marlex high-density polyethylene, Marlexlow-density polyethylene, linear low density polyethylene (for exampleREXELL®), polyester, polybutylene terephthalate (PBT), polyethyleneterephthalate (PET), polytrimethylene terephthalate, polyethylenenaphthalate (PEN), polyetheretherketone (PEEK), polyimide (PI),polyetherimide (PEI), polyphenylene sulfide (PPS), polyphenylene oxide(PPO), poly paraphenylene terephthalamide (for example, KEVLAR®),polysulfone, nylon, nylon-12 (such as GRILAMID® available from EMSAmerican Grilon), perfluoro(propyl vinyl ether) (PFA), ethylene vinylalcohol, polyolefin, polystyrene, epoxy, polyvinylidene chloride (PVdC),poly(styrene-b-isobutylene-b-styrene) (for example, SIBS and/or SIBS50A), polycarbonates, ionomers, biocompatible polymers, other suitablematerials, or mixtures, combinations, copolymers thereof, polymer/metalcomposites, and the like. In some embodiments the sheath can be blendedwith a liquid crystal polymer (LCP). For example, the mixture cancontain up to about 6 percent LCP.

Some examples of suitable metals and metal alloys include stainlesssteel, such as 304V, 304L, and 316LV stainless steel; mild steel;nickel-titanium alloy such as linear-elastic and/or super-elasticnitinol; other nickel alloys such as nickel-chromium-molybdenum alloys(e.g., UNS: N06625 such as INCONEL® 625, UNS: N06022 such as HASTELLOY®C-22®, UNS: N10276 such as HASTELLOY® C276®, other HASTELLOY® alloys,and the like), nickel-copper alloys (e.g., UNS: N04400 such as MONEL®400, NICKELVAC® 400, NICORROS® 400, and the like),nickel-cobalt-chromium-molybdenum alloys (e.g., UNS: R30035 such asMP35-N® and the like), nickel-molybdenum alloys (e.g., UNS: N10665 suchas HASTELLOY® ALLOY B2®), other nickel-chromium alloys, othernickel-molybdenum alloys, other nickel-cobalt alloys, other nickel-ironalloys, other nickel-copper alloys, other nickel-tungsten or tungstenalloys, and the like; cobalt-chromium alloys; cobalt-chromium-molybdenumalloys (e.g., UNS: R30003 such as ELGILOY®, PHYNOX®, and the like);platinum enriched stainless steel; titanium; combinations thereof; andthe like; or any other suitable material.

In at least some embodiments, portions or all of stents 10, 510 andother components of stent 10 and stent 510 may also be doped with, madeof, or otherwise include a radiopaque material. Radiopaque materials areunderstood to be materials capable of producing a relatively brightimage on a fluoroscopy screen or another imaging technique during amedical procedure. This relatively bright image aids the user of stent10 in determining its location. Some examples of radiopaque materialscan include, but are not limited to, gold, platinum, palladium,tantalum, tungsten alloy, polymer material loaded with a radiopaquefiller, and the like. Additionally, other radiopaque marker bands and/orcoils may also be incorporated into the design of guidewire 10 toachieve the same result.

In some embodiments, a degree of Magnetic Resonance Imaging (MRI)compatibility is imparted into stent 10. For example, stents 10, 510 andother components of stent 10 and stent 510, or portions thereof, may bemade of a material that does not substantially distort the image andcreate substantial artifacts (e.g., gaps in the image). Stent 10 andstent 510 and other components of stent 10 and stent 510, or portionsthereof, may also be made from a material that the Mill machine canimage. Some materials that exhibit these characteristics include, forexample, tungsten, cobalt-chromium-molybdenum alloys (e.g., UNS: R30003such as ELGILOY®, PHYNOX®, and the like),nickel-cobalt-chromium-molybdenum alloys (e.g., UNS: R30035 such asMP35-N® and the like), nitinol, and the like, and others.

It should be understood that this disclosure is, in many respects, onlyillustrative. Changes may be made in details, particularly in matters ofshape, size, and arrangement of steps without exceeding the scope of thedisclosure. This may include, to the extent that it is appropriate, theuse of any of the features of one example embodiment being used in otherembodiments. The disclosure's scope is, of course, defined in thelanguage in which the appended claims are expressed.

What is claimed is:
 1. A method of treating a body lumen, the methodcomprising: advancing a retrieval stent into the lumen of an implantedstent disposed along an inner surface of the body lumen, wherein aportion of tissue defining the inner surface of the body lumen has growninto the implanted stent, and wherein the implanted stent includes: aliner disposed within the lumen of the implanted stent, wherein theliner is configured to be radially spaced from a medial region of theimplanted stent to define a tissue ingrowth region along a portion ofthe implanted stent; deploying the retrieval stent within the lumen ofthe implanted stent, wherein an outer surface of the retrieval stentexerts an outward radial force along the ingrown tissue region of theimplanted stent, and wherein the retrieval stent causes the ingrowntissue to recede.
 2. The method of claim 1, wherein the outer surface ofthe retrieval stent is defined by a polymeric covering.
 3. The method ofclaim 2, wherein the retrieval stent includes a radially expandablescaffold and the polymeric covering extends across interstices of theradially expandable scaffold.
 4. The method of claim 3, wherein theradially expandable scaffold is self-expandable.
 5. The method of claim4, wherein the radially expandable scaffold includes a first end regionand a second end region, wherein the tissue ingrowth region extendsbetween the first end region and the second end region.
 6. The method ofclaim 5, wherein the liner is in direct contact with the first andsecond end regions, thereby preventing tissue ingrowth along the firstand second end regions.
 7. The method of claim 5, wherein the linerextends from the first end region to the second end region.
 8. Themethod of claim 5, wherein the medial region has a diameter, and thefirst and second end regions have a diameter greater than the diameterof the medial region.
 9. The method of claim 5, wherein a first endportion of the liner forms an outer layer disposed radially outward ofan outer surface of the first end region, and a second end portion ofthe liner forms an outer layer disposed radially outward of an outersurface of the second end region.
 10. The method of claim 1, whereindeploying the retrieval stent within the lumen of the implanted stentincludes placing the retrieval stent through the lumen of the implantedstent such that the retrieval stent spans an entire length of the tissueingrowth region.
 11. The method of claim 1, further comprising:extracting the implanted stent with the retrieval stent from the bodylumen.
 12. The method of claim 11, wherein extracting the implantedstent with the retrieval stent includes radially constraining a proximalend of the implanted stent.
 13. The method of claim 12, wherein radiallyconstraining the proximal end of the implanted stent includes graspingthe proximal end of the implanted stent with a retrieval device.
 14. Themethod of claim 11, wherein the step of extracting the implanted stentis performed within 2 weeks or less after deploying the retrieval stentwithin the lumen of the implanted stent.
 15. The method of claim 11,wherein the step of extracting the implanted stent is performed between7 days and 14 days after deploying the retrieval stent within the lumenof the implanted stent.
 16. The method of claim 1, wherein deploying theretrieval stent within the lumen of the implanted stent pushes a medialregion of the liner radially outward toward the implanted stent.
 17. Themethod of claim 1, wherein the tissue ingrowth region includes at leasttwo circumferential tissue ingrowth regions spaced-apart longitudinallyalong the medial region of the implanted stent.
 18. A system fortreating a body lumen, comprising: a first stent including: a firsttubular scaffold, the first tubular scaffold including an inner surface,an outer surface, a first end region, a second end region, a medialregion extending between the first end region and the second end region,and a lumen extending from the first end region to the second endregion; and a liner disposed within the lumen of the first tubularscaffold, wherein first regions of the inner surface of the firsttubular scaffold are in direct contact with first portions of the liner,thereby preventing tissue ingrowth, and second regions of the innersurface of the first tubular scaffold are spaced-apart from the linerthereby defining tissue ingrowth regions; and a second stent including:a second tubular scaffold and a covering disposed on the second tubularscaffold; wherein the second stent is configured to be positioned withinthe first stent such that expansion of the second stent causes thetissue ingrowth to recede.
 19. The system of claim 18, wherein the firstportions of the liner are secured to the inner surface of the firsttubular scaffold at a plurality of spaced-apart discrete attachmentpoints.
 20. The system of claim 19, wherein regions of the liner betweenthe plurality of spaced-apart discrete attachment points are radiallyspaced from the inner surface of the first tubular scaffold, creatingthe tissue ingrowth regions.